Chest
Clinical InvestigationsEffects of Inhalation of β2-Sympathicomimetic and Anticholinergic Agents on the Impedance of the Respiratory System in Normal Subjects
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SUBJECTS AND METHODS
We have studied 20 healthy nonsmoking subjects, ten women and ten men, with a mean age of 24 years (range, 22 to 31 years). All subjects had normal basal impedance (Z) values, as determined by an absence of frequency dependence of resistance (R), and a resonant frequency (fo) lower than 16 Hz.
Studies were performed on each subject in a randomized double-blind crossover manner on two separate days at least two days apart, and always at the same time of the day. Impedance of the respiratory
RESULTS
The values of Rrs and Xrs before and after fenoterol are illustrated in Table 1 and values of Rrs and Xrs before and after ipratropium bromide are illustrated in Table 2. The values of Rrs and Xrs under basal conditions were not significantly different between the two study days. As illustrated in Tables 1 and 2, Rrs values increased with frequency.
After inhalation of fenoterol, a highly significant decrease in Rrs values could be observed at all frequencies (Table 1). The values of Xrs were
DISCUSSION
In the present study the resistance and reactance of the total respiratory system was measured simultaneously from 4 to 52 Hz. As was shown by Nagels et al,26 valid conclusions can be drawn for resistance and reactance of the lungs from the values of Rrs and Xrs without partitioning Zrs into the impedance of the lungs and the impedance of the chest wall. We studied the effects of cholinergic receptor blockade and β2-sympathicomimetic receptor stimulation on the impedance of the respiratory
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Manuscript received April 21; revision accepted October 9.